Ingo,
following the conversation on "a redundant reschedule call in set_user_prio()",
here is a possible approach.
The patch is somewhat intrusive as it even dares to adapt TASK_PREEMPTS_CURR().
Nevertheless, this adaptation seems to be ok with all the current use-cases.
Presupposition: TASK_PREEMPTS_CURR(p, rq) will /never/ be used as "a
mere prio comparator" - e.g. to make decisions on which array a task
has to be placed in.
=====
o Make TASK_PREEMPTS_CURR(task, rq) return "true" only if the task's
prio is higher than the current's one and the task is in the "active"
array.
This ensures we don't make redundant resched_task() calls when the
task is in the "expired" array (as may happen now in set_user_prio(),
rt_mutex_setprio() and pull_task() ) ;
o generilise conditions for a call to resched_task() in
set_user_nice(), rt_mutex_setprio() and sched_setscheduler()
Signed-off-by: Dmitry Adamushko <[EMAIL PROTECTED]>
--
--- linux-2.6.21-rc5/kernel/sched-orig.c 2007-04-04
18:26:19.000000000 +0200
+++ linux-2.6.21-rc5/kernel/sched.c 2007-04-04 18:26:43.000000000 +0200
@@ -168,7 +168,7 @@ unsigned long long __attribute__((weak))
(MAX_BONUS / 2 + DELTA((p)) + 1) / MAX_BONUS - 1))
#define TASK_PREEMPTS_CURR(p, rq) \
- ((p)->prio < (rq)->curr->prio)
+ (((p)->prio < (rq)->curr->prio) && ((p)->array == (rq)->active))
#define SCALE_PRIO(x, prio) \
max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 2), MIN_TIMESLICE)
@@ -3847,13 +3847,13 @@ void rt_mutex_setprio(struct task_struct
struct prio_array *array;
unsigned long flags;
struct rq *rq;
- int oldprio;
+ int delta;
BUG_ON(prio < 0 || prio > MAX_PRIO);
rq = task_rq_lock(p, &flags);
- oldprio = p->prio;
+ delta = prio - p->prio;
array = p->array;
if (array)
dequeue_task(p, array);
@@ -3869,13 +3869,10 @@ void rt_mutex_setprio(struct task_struct
enqueue_task(p, array);
/*
* Reschedule if we are currently running on this runqueue and
- * our priority decreased, or if we are not currently running on
- * this runqueue and our priority is higher than the current's
+ * our priority decreased, or if our priority became higher
+ * than the current's.
*/
- if (task_running(rq, p)) {
- if (p->prio > oldprio)
- resched_task(rq->curr);
- } else if (TASK_PREEMPTS_CURR(p, rq))
+ if (TASK_PREEMPTS_CURR(p, rq) || (delta > 0 &&
task_running(rq, p)))
resched_task(rq->curr);
}
task_rq_unlock(rq, &flags);
@@ -3923,10 +3920,11 @@ void set_user_nice(struct task_struct *p
enqueue_task(p, array);
inc_raw_weighted_load(rq, p);
/*
- * If the task increased its priority or is running and
- * lowered its priority, then reschedule its CPU:
+ * Reschedule if we are currently running on this runqueue and
+ * our priority decreased, or if our priority became higher
+ * than the current's.
*/
- if (delta < 0 || (delta > 0 && task_running(rq, p)))
+ if (TASK_PREEMPTS_CURR(p, rq) || (delta > 0 &&
task_running(rq, p)))
resched_task(rq->curr);
}
out_unlock:
@@ -4153,13 +4151,10 @@ recheck:
__activate_task(p, rq);
/*
* Reschedule if we are currently running on this runqueue and
- * our priority decreased, or if we are not currently running on
- * this runqueue and our priority is higher than the current's
+ * our priority decreased, or our priority became higher
+ * than the current's.
*/
- if (task_running(rq, p)) {
- if (p->prio > oldprio)
- resched_task(rq->curr);
- } else if (TASK_PREEMPTS_CURR(p, rq))
+ if (TASK_PREEMPTS_CURR(p, rq) || (task_running(rq, p)
&& p->prio > oldprio))
resched_task(rq->curr);
}
__task_rq_unlock(rq);
=====
--
Best regards,
Dmitry Adamushko
-
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